Study of depth-dependent tetragonal distortion of quaternary AlInGaN epilayer by Rutherford backscattering/channeling

A 240-nm thick Al_0.4In_0.02Ga_0.58N layer is grown by metal organic chemical vapour deposition, with an over 1-μ m thick GaN layer used as a buffer layer on a substrate of sapphire (0001). Rutherford backscattering and channeling are used to characterize the microstructure of AlInGaN. The results show a good crystalline quality of AlInGaN (χ_min=1.5%) with GaN buffer layer. The channeling angular scan around an off-normal <12^{-13> axis in the {101-0} plane of the AlInGaN layer is used to determine tetragonal distortion e_T, which is caused by the elastic strain in the AlInGaN. The resulting AlInGaN is subjected to an elastic strain at interfacial layer, and the strain decreases gradually towards the near-surface layer. It is expected that an epitaxial AlInGaN thin film with a thickness of 850 nm will be fully relaxed (e_T = 0).}     

Tetragonal distortion of InAsPSb film grown on InAs substrate studied by Rutherford backscattering/channeling and synchrotron X-ray diffraction

Rutherford backscattering/channeling spectrometry and synchrotron X-ray diffraction are employed to characterize the structural properties of the InAsPSb epilayer grown on the InAs substrate. The results indicate that a 975-nm thick InAs_0.668P_0.219Sb_0.113 layer has a quite good crystalline quality (χ_min=6.1%). The channeling angular scan around an off-normal 〈1 1 1〉 axis in the (0 1? 1) plane of the sample is used to determine the tetragonal distortion e_T, which is caused by elastic strain in the layer. The results show that the InAsPSb layer is subjected to an elastic strain at the interfacial layer, and the strain decreases gradually moving towards the near-surface layer. It is expected that an epitaxial InAsPSb layer with the thickness of around 1700 nm will be fully relaxed (e_T=0). The magnitude difference of e_T deduced from angular scans and X-ray diffraction implies some structure (like dislocations) may play a role.     

Characterization of tetragonal distortion in a thick Al0.2Ga0.8N epilayer with an AIN interlayer by Rutherford backscattering/channeling

An Al0.2Ga0.8N/AlN/Al0.2Ga0.8N heterostructure was grown by metalorganic chemical vapor deposition on a sapphire （0001） substrate with a thick （〉 1 μm） GaN intermediate layer. The Al composition was determined by Rutherford backscattering （RBS）. Using the channeling scan around an off-normal [1213] axis in the （1010） plane of the Al0.2Ga0.8N layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, is investigated. The results show that eT in the high-quality Al0.2Ga0.8N layer is dramatically released by the AIN interlayer from 0.66% to 0.27%.     

Characterization of tetragonal distortion in a thick Al_(0.2)Ga_(0.8)N epilayer with an AlN interlayer by Rutherford backscattering/channeling

An Al0.2Ga0.8N/AlN/Al0.2Ga0.8N heterostructure was grown by metalorganic chemical vapor deposition on a sapphire(0001) substrate with a thick(> 1 μm) GaN intermediate layer. The Al composition was determined by Rutherford backscattering(RBS). Using the channeling scan around an off-normal [1213] axis in the(1010) plane of the Al0.2Ga0.8N layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, is investigated. The results show that eTin the high-quality Al0.2Ga0.8N layer is dramatically released by the AlN interlayer from 0.66% to 0.27%.     

Interface defects in GaN/sapphire studied using Rutherford backscattering spectroscopy and channeling

GaN on sapphire was grown by MOCVD technique. Rutherford backscattering spectra together with channeling along [0 0 0 1] axis were recorded to study the defects at the interface. Detailed calculation shows that the defects at GaN/sapphire interface are due to dislocations which are distributed into the whole thickness of the film and are mainly aligned on the growth direction.     

用卢瑟福背散射/沟道技术研究ZnO/Zn0.9Mg0.1O/ZnO异质结的弹性应变

利用卢瑟福背散射/沟道技术对射频等离子体辅助分子束外延法生长在蓝宝石衬底上的ZnO/Zn_0.9Mg_0.1O/ZnO异质结进行了组分分析，并得到了异质结弹性应变随深度的变化，应变由界面向表面逐渐释放，并由负变正，且在ZnO与Zn_0.9Mg_0.1O界面处轻微增大.负的应变是由于ZnO与衬底的晶格失配和热失配，而逐渐变为正值是Zn_0.9Mg_0.1O与ZnO的晶格常数差异及弹性应变的 关键词： 异质结 卢瑟福背散射/沟道 弹性应变 ZnMgO     

H+2，H+3团簇离子在沟道条件下的背散射 质子产额测量

采用卢瑟福背散射方法，测得了每质子能量为650 keV的H⁺₂，H+₃团簇离子在Si晶体<100>和<110>沟道条件下的质子背散射能谱.结果发现，由于H⁺₂，H⁺₃团簇在晶体中的库仑爆炸和团簇效应，H⁺₂的背散射质子产额大于H ⁺的背散射产额，而H^{+< 关键词： 团簇 沟道效应 库仑爆炸 背散射}     

Profiling measurements of metal ion distribution in thin polymer inclusion membranes by Rutherford backscattering spectrometry

Polymer inclusion membranes (PIMs) composed of a homogeneous mixture of cellulose triacetate matrix, 2-nitro-phenyl-octyl-ether as plasticizer and tri-octyl-phosphine-oxyde as carrier were synthesized by the spin coating method. Synthesized membranes were doped with molybdenum metal ions and then characterized by four experimental techniques: thermo gravimetric and differential analyses, scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and Rutherford backscattering (RBS) spectrometry using a 3.2 MeV He⁺ ion beam. The RBS analysis has established both the elemental composition as well as the Mo⁺ metal profiling of the studied PIMs. The experimental irradiation conditions were optimized in order to determine the ion fluence thresholds resulting in measurable changes in elemental composition of membranes. Changes in physico-chemical properties of the irradiated PIMs vs He⁺ ion fluence were observed with the ATR-FTIR analysis. Also, the SEM analysis of PIMs surfaces has revealed a porous texture, while the thermal analysis of annealed PIMs at 105°C has showed no significant changes of mass (～1%) of the studied samples.     

Mg+注入对GaN晶体辐射损伤的研究

在蓝宝石衬底上通过金属有机物化学气相沉积(metal-organic chemical vapor deposition，MOCVD)方法外延生长的GaN薄膜具有良好的结晶品质，χ_min达到2.00%. 结合卢瑟福背散射/沟道(Rutherford backscattering/channeling，RBS/C)和高分辨X射线衍射(high-resolution X-ray diffraction，HXRD)的实验测量，研究了不同剂量和不同角度Mg⁺注入GaN所造成的辐射损伤. 实验结果表明，随注入剂量的增大，晶体的辐射损伤也增大，注入剂量在1×10¹⁵atom/cm²以下，χ_min小于4.78%，1×10¹⁶atom/cm²是Mg⁺注入GaN的剂量阈值，超过这个阈值，结晶品质急剧变差，χ_min达到29.5%；随机注入比沟道注入的辐射损伤大，且在一定范围内随注入角度的增大，损伤也增大，在4×10¹⁵atom/cm²剂量下偏离〈0001〉沟道0°，4°，6°，9°时的χ_min(%)分别为6.28，8.46，10.06，10.85；经过700℃/10min+1050℃/20s两步退火和1000℃/30s高温快速退火后，晶体的辐射损伤都有一定程度的恢复，而且1000℃/30s高温快速退火的效果更好，晶体的辐射损伤可以得到更好的恢复. 关键词： GaN 卢瑟福被散射/沟道 高分辨X射线衍射 辐射损伤     

AlxGa1-xN晶体薄膜中铝含量的卢瑟福背散射精确测定

采用金属有机化合物气相淀积法在(0001)取向的蓝宝石衬底上生长一层 大约20 nm厚的AlN缓冲层, 在缓冲层上生长大约2 μm厚、 晶体质量良好的Al_xGa_1-xN外延层, 通过深紫外光致发光法测量发光峰的能量E_g 判断外延层中铝含量的均匀性, 取样品均匀性良好的氮铝镓外延片进行卢瑟福背散射(RBS)实验, 通过两个高能离子束实验室分别进行RBS随机谱分析, 每个实验室测量六个样品, 由分析软件拟合随机谱获得外延层中的x_Al. 并对样品的均匀性、堆积校准、计数统计、散射角、离子束能量与阻止截面 等影响测量结果准确性的不确定度来源进行分析. 结果表明, 采用入射离子⁴He, 能量为2000 keV, 散射角为165° 时, 氮铝镓外延片中铝含量(x=0.8) 的测量不确定度为2.0%, 包含扩展因子k=2. 关键词： 氮铝镓 卢瑟福背散射 测量不确定度 金属有机化合物气相淀积法     

Heusler合金Mn2 NiAl的电子结构和磁性对四方畸变的响应及其压力响应

运用基于密度泛函理论的第一性原理的投影缀加波方法,对Hg₂CuTi型Mn₂NiAl在由立方结构至四方结构的畸变过程中电子结构和磁性的变化规律及其对压力响应的规律进行了研究.研究发现:在由奥氏体相到马氏体相的相变中,由于Ni-Mn(A)原子间距的减小而使得杂化程度增强,导致占据态的态密度向低能区域移动,体系的能量降低,致使在马氏体相中的稳定性增大;在从奥氏体相到马氏体相的相变中,能带变宽,成键作用加强,从而在马氏体相中的稳定性增大;在四方畸变过程中,总磁矩的变化主要来源于Ni原子磁矩的变化;计算得到Mn₂NiAl的零压体积弹性模量为125.69 GPa,其抗压缩性比其他常见的Heusler型合金弱. 关键词： 第一性原理 电子结构 磁性 四方畸变     

Investigations on the oxidation of zirconium nitride films in air by nuclear reaction analysis and backscattering spectrometry

The thermal oxidation of dc magnetron sputter deposited thin ZrN films in air in the temperature range of 100-475 °C has been studied by depth profiling N using nuclear reaction analysis (NRA) involving ¹⁵N(¹H,αγ)¹²C resonance reaction and O using 3.05 MeV ¹⁶O(α,α)¹⁶O resonant scattering. The structural and morphological changes accompanying the process have also been investigated. NRA/backscattering spectrometry measurements show that oxidation results in the formation of ZrO_1.8±0.1 at the surface. An interface consisting of Zr, O and N is also formed underneath the surface oxide. For an isothermal annealing, oxide layer as well as interface exhibits parabolic growth with the duration of annealing. The diffusion of oxygen through the already grown oxide layer (D = 5.6 × 10⁻¹⁴ cm² s⁻¹ at 475 °C) forms the rate-controlling step of oxidation. The diffusion may be facilitated by the high concentration of oxygen vacancies in the oxide layer. Glancing incidence X-ray diffraction (GIXRD) measurements indicate that zirconia films formed are phase-singular (monoclinic) and are textured in (2 0 0) and (3 1 1) orientations. Examination by scanning electron microscopy (SEM) reveals the formation of blisters on sample surfaces on prolonged oxidation. The blistering can be attributed to intrinsic growth stress arising due to the larger molar volume of zirconium oxide in comparison to zirconium nitride, a fact demonstrated by the depth profile measurements as well.     

Study of the long-range effect by the method of Rutherford backscattering with ion channeling under light irradiation of silicon

The results of a study of the effect of light irradiation of silicon on the spectra of Rutherford backscattering with ion channeling (RBSC) in the side opposite to the irradiated one are presented. It is shown that the integral yield of backscattered He⁺ ions increases as a result of irradiation (the long-range effect); in this case, the shape of the dependence of the effect size on the irradiation time is bell-like and agrees qualitatively with the results obtained by hardness measurements previously. These data show light generation of a high concentration of movable defects near the opposite plate side.     

Determination of migration of ion-implanted Ar and Zn in silica by backscattering spectrometry

It is well known that the refractive indices of lots of materials can be modified by ion implantation, which is important for waveguide fabrication. In this work the effect of Ar and Zn ion implantation on silica layers was investigated by Rutherford Backscattering Spectrometry (RBS) and Spectroscopic Ellipsometry (SE). Silica layers produced by chemical vapour deposition technique on single crystal silicon wafers were implanted by Ar and Zn ions with a fluence of 1–2?×10¹⁶ Ar/cm² and 2.5?×10¹⁶ Zn/cm², respectively. The refractive indices of the implanted silica layers before and after annealing at 300°C and 600°C were determined by SE. The migration of the implanted element was studied by real-time RBS up to 500°C. It was found that the implanted Ar escapes from the sample at 300°C. Although the refractive indices of the Ar-implanted silica layers were increased compared to the as-grown samples, after the annealing this increase in the refractive indices vanished. In case of the Zn-implanted silica layer both the distribution of the Zn and the change in the refractive indices were found to be stable. Zn implantation seems to be an ideal choice for producing waveguides.     

InGaN/GaN多量子阱的组分确定和晶格常数计算

采用金属有机化学气相沉积(MOCVD)技术以蓝宝石为衬底在n型GaN单晶层上生长了InGaN/GaN多量子阱结构外延薄膜，利用高分辨X射线衍射(HRXRD)，卢瑟福背散射/沟道(RBS/channeling)，以及光致发光(PL)技术对InGaN/GaN多量子阱结构薄膜分别进行了平均晶格常数计算、In原子替位率计算和In组分的定量分析.研究表明：InGaN/GaN多量子阱的水平和垂直方向平均晶格常数分别为a_epi=0.3195nm，c_epi=0.5198nm，In原子的替位率为99.3%，利用HRXRD和RBS/channeling两种分析技术计算In的组分分别是0.023和0.026，并与样品生长时设定的预期目标相符合，验证了两种实验方法的准确性；而用室温条件下的光致发光谱(PL)来计算InGaN/GaN多量子阱中In的组分是与HRXRD和RBS/channeling的实验结果相差很大，说明用PL测试In组分的方法是不适宜的. 关键词： InGaN/GaN多量子阱 高分辨X射线衍射 卢瑟福背散射/沟道 光致发光     

Heusler合金Pd2 CrAl四方变形、磁性及弹性常数的第一性原理计算

采用基于密度泛函理论的投影缀加波方法研究了Heusler合金Pd₂CrAl的四方变形、磁性和弹性常数. 四方变形中,Pd₂CrAl在c/a≈1.20处出现总能的局域最小值,对应一个稳定的马氏体. Pd₂CrAl的L2₁结构和四方结构的单胞总磁矩分别为3.825μ_B和3.512μ_B. 在这两种结构中Cr原子均是Pd₂CrAl总磁矩的主要贡献者,Pd和Cr原子间存在很强的杂化作用,Cr的3d电子的t_2g和e_g两个亚能带是Pd₂CrAl磁性的主要来源. 弹性常数的计算结果显示,Pd₂CrAl的L2₁结构和四方结构的弹性常数均满足相应结构的稳定性判据. 关键词： Heusler合金 四方变形 磁性 弹性常数     

GaSb/GaAs复合应力缓冲层上自组装InAs量子点的生长

研究了GaSb/GaAs复合应力缓冲层上自组装生长的InAs量子点.在2ML GaSb/1ML GaAs复合应力缓冲层上获得了高密度的、沿［100］方向择优分布量子点.随着复合应力缓冲层中GaAs层厚度的不同,量子点的密度可以在1.2×10¹⁰cm^-2和8×10¹⁰cm^-2进行调控.适当增加GaAs层的厚度至5ML,量子点的发光波长红移了约25nm,室温下PL光谱波长接近1300nm. 关键词： 自组装量子点 分子束外延 Ⅲ-Ⅴ族化合物半导体     

利用预失真条纹校正PMP系统投影仪畸变的研究

依据摄像机畸变模型提出了一种投影条纹相位畸变校正方法来简化相位-高度映射关系.该方法首先通过投两套互相垂直的相移正弦条纹,以相位值代替投影仪像素坐标,将投影仪当成摄像机看待,标定出投影仪的内参量.然后根据标定出的投影仪镜头畸变参量对理想相位施加反向的畸变,在投影时反向畸变的光栅通过镜头畸变,又成为理想的光栅,从而简化了相位-高度映射关系.实验中,虽然由于测量误差的影响,校正后的投影仪径向畸变系数还是比原来小了1个数量级.     

Applications of high energy ion beam techniques in environmental science: Investigation associated with glass and ceramic waste forms

High energy ion beam capabilities including Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA) have been very effectively used in environmental science to investigate the ion-exchange mechanisms in glass waste forms and the effects of irradiation in glass and ceramic waste forms in the past. In this study, RBS and NRA along with SIMNRA simulations were used to monitor the Na depletion and D and ¹⁸O uptake in alumina silicate glasses, respectively, after the glass coupons were exposed to aqueous solution. These results show that the formation of a reaction layer and an establishment of a region where diffusion limited ion exchange occur in these glasses during exposure to silica-saturated solutions. Different regions including reaction and diffusion regions were identified on the basis of the depth distributions of these elements. In the case of ceramics, damage accumulation was studied as a function of ion dose at different irradiation temperatures. A sigmoidal dependence of relative disorder on the ion dose was observed. The defect-dechanneling factors were calculated for two irradiated regions in SrTiO₃ using the critical angles determined from the angular yield curves. The dependence of defect-dechanneling parameter on the incident energy was investigated and it was observed that the generated defects are mostly interstitial atoms and amorphous clusters. Thermal recovery experiments were performed to study the damage recovery processes up to a maximum temperature of 870 K.